@Sylvain
My apologies - that was an assumption I should not have made. With that said, your numbers do not prove that more people have been participating, they prove that more posts have been made.
@ all
What we are trying to fix is the user friendliness of the system, and the public facing aspect of the group. Right now, for non-members, it is incredibly painful trying to find out anything that the group has been discussing because of the poor way in which the conversations are exposed online. It's also off-putting from most web designers to have to go through the list process to join.
To put my "being questionably generalist" hat on again - I expect that using these archaic communication methods attracts a certain type of person and puts off another. Sadly I think it's the designer types that get put off, and yet it is those people for whom we are making CSS. Engineer types and/or network enthusiasts seem less put off.